The present disclosure relates to a gas turbine engine and, more particularly, to a heat shield arrangement therefor.
Thermal shields are used in gas turbine engines to thermally isolate particular structures from an active heat transfer environment. The effectiveness of these shields, which may be a combination of a metal foil backing enclosing an insulation type blanket next to the structure, is directly dependent upon having no gaps or channels between the blanket and the structure and upon the blankets retaining their original shape. Gaps or channels between the blanket and the structure have an inherent “flow leak.” Leaks have an associated flow velocity that can generate a significant heat transfer coefficient. Gaps between the heat shield and engine case structure allow fluid to flow out of the case structure.
Thermal distortions and part-to-part tolerances may compromise the ability of the heat shield to operate as an effective seal. Most heat shields used in standard turbine/compressor design applications, have an “inside” radial fit-up. This radial fit-up is not readily controlled effectively during engine transient operation. In addition, vibration of the engine structure can cause the fibrous insulation blanket to deteriorate and lose shape thereby providing a flow path between the blanket and the structure insulated by the blanket.